AICHE JOURNAL
·
2022
·Vol. 68
·期 7
·e17679
·
IF 4.167
Jun Liang,Lei Ni,Peihong Wu,Hang Yao,Qiang Chen,Gang Fu,Juncheng Jiang
In this study, different calorimetric and analytical techniques were used to evaluate the thermal behavior of the preparation of 1-nitronaphthalene through the nitration of naphthalene with mixed acid. Differential scanning calorimetry and adiabatic calorimetry revealed that 1-nitronaphthalene lacks thermal decomposition characteristics. The results of reaction calorimetry, high-performance liquid chromatography, and the density function theory method were combined to analyze the reaction mechanism. An expanded Stoessel criticality diagram was developed to evaluate the process safety of the semibatch nitration reaction. The results revealed a higher degree of risk than that obtained when using the traditional Stoessel criticality diagram. Kinetics parameters of the reaction were investigated.
研究领域:
化学工程
·
工艺安全
✓ 已验证
产品关联
DOI
高影响因子
WASTE MANAGEMENT
·
2023
·
IF 8.1
Cong Li,Xiaofeng Yang,Yongkui Li,Yu Chen,Xiaodong Pan,Yongping Xie,Xingyu Liu,Suqin Li
Hematite tailings (HTs) are rich in silica and are used as replacements for fine aggregates in the preparation of construction materials. However, there is scope for a more effective utilization of the valuable elements present in HTs. In this paper, a process for preparing high-purity SiO 2 using HTs procured from Ansteel (China) is proposed. HTs were treated using the superconducting high-gradient magnetic separation (S-HGMS) technology, where the silica as part of the nonmagnetic fraction was obtained in the form of a high-silica concentrate, which was then subjected to mixed-acid leaching to dissolve impurities to achieve refined purification. The optimum process conditions for S-HGMS were determined, and the response surface methodology was applied to optimize the process parameters of the mixed-acid leaching process. The process indicators of the mixed-acid leaching step included the leaching time, leaching temperature, and molar ratio of the mixed acids. The optimum process conditions for S-HGMS were as follows: the magnetic strength-to-velocity ratio in the weak magnetic separation stage was set to 0.034 T·s/m whereas it was maintained at 0.076 T·s/m in the strong magnetic separation stage; the pulp concentration was 40 g/L, the pulp velocity was 500 mL/min, and the dispersant concentration was 1 mg/g. Under these conditions, the high-silica pulp was processed. The corresponding SiO 2 grade increased from 71.788 % to 95.260 %, and its recovery and yield reached 56.330 % and 42.450 %, respectively. The SiO 2 content in the sample increased from 95.260 % to 99.961 %. Further, the mechanisms of the S-HGMS and mixed-acid leaching were revealed. The proposed process is environmentally friendly and operationally inexpensive. It can reduce the amount of HTs by 42.450 %, and the obtained high-purity silica product has high economic value and good industrialization prospects.
研究领域:
材料科学
·
环境工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
AICHE JOURNAL
·
2022
·Vol. 68
·期 4
·e17564
·
IF 4.167
Yongjin Cui,Jing Song,Chencan Du,Jian Deng,Guangsheng Luo
The nitration of chlorobenzene with concentrated mixed acids is a fast and highly exothermic process, which suffers from considerable mass transfer resistance and poor heat transfer rates. The reaction kinetics has not been thoroughly reported before. In this work, a continuous-flow microreactor system and a homogeneous reaction condition were proposed to obtain accurate chlorobenzene nitration kinetics parameters at high mixed acid concentrations. A general model for predicting the observed reaction rate constants was established. With a new method for estimating the equilibria associated with HNO 3 in aqueous sulfuric acid, the rate constants based on nitronium ion and activation energies were obtained. Compared with batch reactors, the continuous-flow microreactor system allows for a sufficient heat transfer efficiency and accurate residence time control, making it possible to study the reaction performance more quickly and sensitively. This work may provide a reliable reference for the kinetic study of similar processes.
研究领域:
化学工程
·
物理化学
·
反应工程
✓ 已验证
产品关联
DOI
高影响因子
PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
·
2023
·
IF 7.8
Hang Yao,Lei Ni,Yinshan Liu,Gang Fu,Juncheng Jiang,Zhen Cheng,Yuqing Ni,Zhiquan Chen
The exothermic pattern of m-xylene nitration with mixed acid in semi-batch mode was studied by reaction calorimetry . Adiabatic temperature rise ( Δ T ad ) and reaction enthalpy ( ∆ H ) were obtained to identify the thermal hazard. Process conditions including stirring rate, reaction temperature and strength of mixed acid were studied to optimize the reaction. Optimal yield (95.5%) was reached under the conditions of sufficient stirring rate, 70% strength of mixed acid and reaction temperature of 40 °C. Meanwhile, the thermal stability of nitration products was investigated by differential scanning calorimetry (DSC) and accelerating rate calorimetry (ARC). Pyrolysis kinetic parameters were calculated under non-isothermal and adiabatic conditions . Furthermore, the maximum temperature of the runaway system for synthesis reaction ( MTSR ) was determined to analyze the reaction hazard. The thermal risk of nitration of m-xylene was also assessed by the risk matrix and Stoessel criticality diagram. In addition, the nitration mechanism of m-xylene was presented. The active site for the electrophilic reaction of m-xylene was predicted via theoretical approach which was in consistent with the selectivity obtained by the experiment. These findings provide guidance for the safe operation of m-xylene nitration and can be used for further scale-up.
研究领域:
化工工程
·
热安全
·
过程优化
·
反应动力学
·
风险评估
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）